Is it normal to wait 50 min for baking a "simple" fluid animation?
This seems quite normal - fluid simulations are very CPU intensive to bake and the workload increases exponentially based on the simulation Resolution (eg, doubling the Resolution results in 8 times the number of 'cells' in the domain (2x2x2)).

If you look closely at the video, shortly after the guy hits 'Bake', the mouse jumps to slightly above the bake button. Most likely he paused the video midway, allowed it to complete the bake, then carried on as if it had only taken seconds - whereas, really, it likely took a similar amount of time as you are experiencing.